tânianess comes from "Tânia", a brazilian version of the female name "Tanja". This name derives from Titus Tatius, who attacked the Ancient Rome after the Rape of the Sabine Women and was with Romulus, after both reconciled, king of the Ancient Rome. Because of Titus' actions the name "Tânia" is especially in the south of Brazil connected with "charity", "honourable" or simply colloquial "amazing".
Therefore, as a memory of him, especially since he isn't counted as one of the traditional "Seven Kings of Rome", "tânianess" is similiar to the word "awesomeness" like the state of being beyond awesome, when there is no fitting word for

But sometimes it's also used ironic, when someone pretends to be a nice and great person.